This invention is directed to polyarylate molding compositions and molded are made therefrom having improved mechanical properties.
Linear aromatic polyesters prepared from dicarboxylic acids, especially from aromatic dicarboxylic acids and bisphenols are well known for their suitability for molding, extrusion, casting, and film-forming applications. For example, U.S. Pat. No. 3,216,970 to Conix, discloses linear aromatic polyesters prepared from isophthalic acid, terephthalic acid, and a bisphenolic compound. Such high molecular weight compositions are known to be useful in the preparation of various films and fibers. Further, these compositions, when molded into useful articles using conventional techniques, provide properties superior to articles molded from other linear polyester compositions. For instance, aromatic polyesters are known to have a variety of useful properties, such as good tensile, impact, and bending strengths, high thermal deformation and thermal decomposition temperatures, resistance to UV irradiation and good electrical properties.
Present state of the art concerns have been to impart desired physical properties to polyarylate resins by inclusion of additives. For example, the impact properties of polyarylates have been increased by the addition of vinyl impact modifiers. A wide variety of impact modifiers, based on rubbers of polybutadiene, butadiene-styrene copolymers, etc., as well as hydrocarbon based elastomers have been suggested as additives to polyarylates to increase the impact properties of the polymers.
U.S. Pat. No. 3,792,118 discloses a composition comprising 1 to 95% by weight of a styrene resin and about 99 to 5% by weight of a polyarylene ester.
U.S. Pat. No. 4,231,922 is specifically directed to improving the notched izod impact values of polyarylate molding compositions by the addition of a polyalkylene terephthalate and an impact modifier thereto. The impact modifiers comprise SAN copolymers grafted onto an unsaturated elastomeric backbone and have a tensile modulus of less than 100,000 psi.
U.S. Pat. No. 4,281,079 also discloses improving the impact resistance of polyarylene esters by incorporating impact modifiers comprising an elastomeric ethylene 1-alkene copolymer such as ethylene and propylene or 1-butene.
U.S. Pat. No. 4,199,493 discloses improving the processability of reinforced polyarylene esters by intimately blending a polyarylene ester, a reinforcing agent and a vinyl addition polymer.
It is also known that the improvement of an engineering plastic such as polyarylate in terms of moldability by polymer blending tends to involve the thermal stability of the resin. Also, the improvement of chemical resistance tends to lead to a reduction in heat distortion temperature. Therefore, a polyarylate resin composition which retains good thermal stability inherent in the resin and further has good moldability and thermal resistance has long been desired.
U.S. Pat. No. 4,123,420 broadly states that the polyarylate compositions may contain at least one additional polymer such as polyalkylene terephthalates (e.g. polyethylene terephthalate or polybutylene terephthalate), poly(ethylene oxybenzoate), polycarbonates, polyethylene, polypropylene, polyamides, polyurethanes, polystyrene, ABS resins, EVA copolymers, polyacrylates, polytetrafluoroethylene, polymethyl methacrylates, polyphenylene sulfide, and rubbers.
U.S. Pat. No. 4,286,075 discloses a blend of a polyarylate and a thermoplastic polymer including polyalkylene terephthalates, polycarbonates, styrene polymers, alkylacrylate polymers, polyurethane, polyvinylchloride polymers, a polyarylether, a copolyetherester block polymer or a polyhydroxyether.
A blend of polyarylates and polyamides are disclosed in U.S. Pat. Nos. 4,052,481; 4,206,100; 4,254,242 and 4,258,154, all assigned to Unitika Limited, Japan.
Although not directed to polyarylates, U.S. Pat. No. 4,547,547 discloses improving the impact resistance and crystallization velocity of polyalkylene terephthalates by blending the polyester with a minor amount of a segmented polyesteramide. The polyesteramides are those which are described in U.S. Pat. No. 4,129,715 and are those which are used in the present invention which is more fully described below.
U.S. Pat. No. 4,279,801 also discloses a blend of a polyalkylene terephthalate and a thermoplastic poly(ester-urethane) elastomer.
It would be advantageous to impart to polyarylates characteristics not inherent in polyarylate resins or to improve upon particular physical properties without adversely affecting the desirable physical and chemical properties of polyarylates such as the inherent UV stability and high heat distortion temperature.